Airbag systems in vehicles often are fashioned to deploy all airbags when a crash occurs. If the passenger seat is empty or contains a child or other small occupant it is desirable to inhibit deployment since the airbag deployment may be useless or even counterproductive. It is thus necessary to detect whether a large occupant is present.
One approach to detecting occupant size is to employ a sensor in the seat cushion and measure weight on the cushion surface. This does not measure weight on the seat back which makes the solution less accurate.
Another approach is to attach load cells between the seat frame and the seat track at the mounting locations. This measures the seat back weight but requires redesign of the seat; otherwise the addition of load cells would change the effective height of the seat. Also attachment between the seat frame and the seat track makes the load cell a structural component which requires reevaluation of the seat design to assure that crash worthiness requirements are met.